Cheung Sha Wan -- Hong Kong's only wholesale poultry market --- is now shut for 21 days for disinfection and the sale of live birds in the city has ground to a halt on the eve of the Lunar New Year holiday season.

So far this year, China has confirmed 110 human H7N9 cases including 22 deaths, according to an AFP tally of reports by local authorities.

In the worst-hit province of Zhejiang, three members of the same family contracted the H7N9 strain, the official Xinhua news agency reported late Tuesday.

Hong Kong health authorities said a total of 254 H7N9 cases have been confirmed on the mainland since the outbreak began there in February 2013, sparking fears the virus could mutate to become easily transmissible between people, potentially triggering a pandemic.

An additional four cases have been confirmed in Hong Kong, three of them fatal.